WO2011074856A2

WO2011074856A2 - Method and apparatus for supporting a handover in a broadband wireless access communication system

Info

Publication number: WO2011074856A2
Application number: PCT/KR2010/008938
Authority: WO
Inventors: 이대우
Original assignee: 삼성전자 주식회사
Priority date: 2009-12-15
Filing date: 2010-12-14
Publication date: 2011-06-23
Also published as: US8843140B2; WO2011074856A3; KR20110068119A; US20130029670A1

Abstract

The present invention relates to a broadband wireless access communication system, and particularly, to a method for supporting a handover in a broadband wireless access communication system. A method for performing a handover in a broadband wireless access communication system according to one embodiment of the present invention comprises: a step in which a macro base station consists of mapping information using base station IDs (BS-IDs) used by a plurality of femto base stations and transmission-related information, and transmits the mapping information to the plurality of femto base stations; and a step in which the macro base station performs, using the mapping information, a handover in which one of the plurality of femto base stations is set as a target base station, upon receipt of a handover request from a terminal.

Description

Method and apparatus for supporting handover in broadband wireless communication system

The present invention relates to a broadband wireless communication system, and more particularly, to a method and apparatus for supporting handover in a broadband wireless communication system.

The 4th Generation (hereinafter referred to as '4G') communication system provides users with services of various quality of service (QoS) using a transmission rate of about 100 Mbps. There is active research going on. Particularly, in 4G communication systems, studies are being actively conducted to support high-speed services in a form of guaranteeing mobility and QoS in a broadband wireless access (BWA) communication system such as a wireless local area network network system and a wireless urban area network system. Is going on. The representative communication system is the Institute of Electrical and Electronics Engineers (IEEE) 802.16 system.

1 illustrates a macro cell in which a plurality of femtocells are installed in an IEEE 802.16 system.

Referring to FIG. 1, a plurality of macro cells C-10 formed by the first macro base station 10 and a second macro cell C-20 formed by the second macro base station 20 may be provided. The femtocell is configured.

When the terminal enters the coverage of the other base station from the serving base station provided with the service, handover is performed to receive continuous service. At this time, the terminal reselects a newly entered base station. As a handover method, in the IEEE 802.16e system, the terminal receives a neighbor base station list from a serving base station, searches for neighbor base stations using the neighbor base station list, and performs handover. Determine the target base station.

In order to support fast handover, the first macro BS 10 registers a neighboring second macro BS 20 and other macro base stations in a neighbor list.

The first macro BS 10 includes radio configuration information of each of the neighbor base stations as well as a list of neighbor base stations in the neighbor list. In addition, the first macro BS 10 delivers the neighbor list to terminals located in a cell by adding a BS ID (Base Station IDentifier) of neighbor BSs in a MOB_NBR-ADV (MOBile_NEighBor-ADVertisement) broadcast message. do.

Accordingly, the terminals periodically measure the signals of the neighboring base stations, and can perform a quick handover by utilizing them. The terminal receives a center frequency, a bandwidth, an FFT size, a preamble index, and a frame of a neighboring base station obtained through the MOB_NBR-ADV received from a serving base station to which the terminal is connected. Received Signal Strength Indicator (RSSI) and Carrier to Interference and Noise Ratio (CINR) for each neighboring base station are measured using information such as frame duration and BS_EIRP (Base Station Equivalent Isotropically Radiated Power). The RSSI and CINR of the neighbor base station are compared with the RSSI and CINR of the serving base station, and one or more neighbor base stations are used to select a target base station for handover according to the comparison result. Therefore, the TX power of the base station included in the neighbor list is a necessary factor for the normal handover decision of the UE. However, the WiMAX standard limits the number of neighbor lists available to one base station to 255, and all base stations must use a unique base station identifier (BS-ID). Therefore, if there are multiple Pico or Femto BSs in one macro BS area, since normal handover cannot be provided to the terminal due to the limitation of the number of neighbor lists, the number of BS-IDs included in the neighbor list is overcome. An alternative for performing a smooth handover should be proposed.

Accordingly, the present invention provides a method and apparatus for overcoming the limitation of the number of base station identifiers (BSIDs) that can be included in a neighbor list in a broadband wireless communication system.

In addition, the present invention provides a method and apparatus for improving handover performance of a terminal through control of Femto / Pico BS parameters (eg, TX power level, etc.) when multiple base stations use the same BSID in a broadband wireless communication system. .

In addition, the present invention, when the Femto / Pico BS is automatically initialized by the SON (Self Organization Network) method, the macro BS air / MAC (Medium Access Control, referred to as "MAC") configuration of the Femto / Pico BS (configuration) Provided are a method and an apparatus for efficiently obtaining information.

In the method according to an embodiment of the present invention, in the macro base station of the broadband communication system handover method, the macro base station by using the information related to the base station ID (BS-ID) and power used by a plurality of lower base stations, Configuring mapping information, transmitting the mapping information to the plurality of lower base stations, and when a handover request is received from a terminal, handover one of the plurality of lower base stations to a target base station using the mapping information. It includes the process of performing.

An apparatus according to an embodiment of the present invention is a macro base station apparatus performing a handover in a macro base station of a broadband communication system, and mapping using information related to base station IDs (BS-IDs) and powers used by a plurality of lower base stations. When information is configured, the mapping information is transmitted to the plurality of lower base stations, and when a handover request is received from a terminal, handover is performed using one of the plurality of lower base stations as a target base station using the mapping information. It includes a control unit.

According to the present invention, in a situation where a plurality of base stations use the same BSID in a broadband wireless communication system, the UE can smoothly handover in an area where a plurality of base stations are concentrated through control of Femto / Pico BS parameters (eg, TX power level). Can be done.

In addition, the present invention can support efficient handover when a plurality of femto / pico BSs exist in the area serviced by the Macro BS.

In addition, according to the present invention, when the Femto / Pico BS is automatically initialized in the SON method, the macro BS can efficiently acquire air / MAC configuration information of the Femto / Pico BS.

In addition, the present invention can enable a smooth handover even in a region where the BS is dense, as well as the standard interface of the macro network, without changing the air interface between the femto base station and the existing terminal.

1 illustrates a macro cell in which a plurality of femtocells are installed in an IEEE 802.16 system;

2 is a diagram illustrating an example of a neighbor list of a macro BS in a general broadband wireless communication system;

3 is a diagram illustrating an example of information on basic configuration parameters for a SON obtained from a SON server or a management server when the BS initializes;

4 is a diagram illustrating an example of a neighbor list of a macro BS in a broadband wireless communication system according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating an example of a BS-ID and configuration parameters in a Femto / Pico BS managed by a macro BS according to an embodiment of the present invention. FIG.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention provides a Femto / Pico BS parameter (eg, TX power) in a situation where a plurality of base stations share a BSID in a broadband wireless communication system. level, etc.), the terminal can perform a smooth handover (handover) in a region where a plurality of base stations are concentrated. In order to control the Femto / Pico BS parameters, in the embodiment of the present invention, a frequency band, TX power, Downlink Channel Descriptor (DCD) CCC, and Uplink Channel that can be used by the Femto / Pico BS Descriptor) Manages by mapping the CCC value with the BS-ID. Hereinafter, in the embodiment of the present invention, a wireless communication system of Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) method is used. An example will be described, and the same may be applied to other wireless communication systems. In addition, the Femto / Pico BS described in the specification of the present invention means that it includes at least one of the Femto BS and Pico BS.

FIG. 2 is a diagram illustrating an example of a neighbor list of a macro BS in a general broadband wireless communication system.

Referring to FIG. 2, the BS-ID used by the femto / pico BS should be unique. The Macro BS needs to know the air / MAC configuration parameters of the Femto BS for handover support to the Femto BS. However, in the case of Femto BS, the system is usually initialized based on the Self Organization Network (SON). Femto BS uses a network separated from Macro network, OAM (Operation, Administration and Maintenance) system separated from Macro network, and a SON server separate from Macro network. Therefore, it is difficult for the Macro BS to acquire the air / MAC configuration parameter information required when configuring the neighbor list for the Femto BS.

3 shows an example of information on basic configuration parameters for a SON obtained from a SON server or a management server when the BS initializes. The obtained information may be BS-ID (optional), frequency band (or center frequency), channel bandwidth (channel BW), transmittable power range (TX capable power range), and the like. The BS determines the BS-ID, the optimal frequency, the transmission power, etc. according to the SON algorithm based on the obtained information. In this case, the BS-ID may be designated by the SON / management server or may be used as a value stored internally.

4 is a diagram illustrating an example of a neighbor list of a macro BS in a broadband wireless communication system according to an exemplary embodiment of the present invention.

A base station (BS) 410 is a system located between the ASN-GW 420 and a mobile terminal. In addition, the base station interfaces with a wireless connection according to the IEEE 802.16 standard to provide a connection to the wireless section to the subscriber, and performs a traffic encryption function of the wireless section.

The base station can be classified into a macro BS, a pico BS, a femto BS, and the like.

A base station controller (ASN-GW: Access Service Network Gateway) 420 is connected to an Internet Protocol Network (not shown) and a base station, respectively, to establish connection and mobility of subscribers. It manages and assigns unique service flow for each up / down (UL / DL) connection.

The ASN-GW 420 may be classified into a macro ASN-GW, a Femto ASN-GW, and the like.

The SON server 430 is a server for supporting air parameter auto-configuration and auto-optimization functions of Femto / Pico BS. In general, SON function is mainly used in Pico BS and Femto BS, but can be used in general macro BS. Here, the SON technology is used to automatically set up the base station configuration when installing a new base station, and to optimize the operation information by exchanging data related to the wireless environment with the base station and the terminal during operation, thereby increasing the capacity of the base station and expanding the coverage. Means technology.

According to the present invention, in a situation where a plurality of base stations share a BSID in a broadband wireless communication system, a terminal can smoothly handover in a region where a plurality of base stations are concentrated through control of a femto / pico BS parameter (TX power level, etc.). In order to be able to do this, three proposals are made.

BS-ID 재사용을 통한 macro BS 이웃 목록 최소화 방법How to minimize macro BS neighbor list by reusing BS-ID

In FIG. 2, all BSs have different BS-IDs. However, in the present invention, as shown in FIG. 4, a plurality of BSs share a BS-ID in an air section. Since a plurality of BSs share a BS-ID in an air section, a limitation of the number of neighbor lists of a macro BS may be overcome. In order to share the BS-ID in the air section, the coverage of the transmission signal transmitted by the BS sharing the BS-ID should not overlap each other. For this purpose, a plurality of shared BS-IDs are defined, and each BS uses a SON function to select the BS-IDs so as not to overlap each other.

In this case, the transmission power of the Femto BS / Pico BS is relatively low, and the Femto BS / Pico BS is often installed indoors. When installed indoors, the radio communication range of Femto BS and Pico BS is very short. Therefore, many Femto / pico BS can reuse the BS-ID used in the air section.

How to improve handover performance by controlling configuration parameters (eg TX power level) of Femto / Pico BS

Simple BS-ID sharing of the Femto BS / pico BS cannot guarantee normal service when the UE is handed over from the macro BS to the pico / Femto BS area. The reason is that when each BS randomly selects transmission power, DCD CCC, and UCD CCC values, the UE cannot select normal transmission power after handover from the macro BS area to the femto / pico BS area. Accordingly, the present invention proposes a method of mapping a frequency band, TX power, DCD CCC, and UCD CCC values that can be used by the Femto / Pico BS with the BS-ID and managing the table. In this case, the transmission power may use a range rather than a specific value. Since all BSs having the same BS-ID have the same transmit power level, DCD CCC, and UCD CCC values, the UE supports a function of selecting normal transmit power even after handover.

FIG. 5 is a diagram illustrating an example of a BS-ID and configuration parameters in a Femto / Pico BS managed by a macro BS according to an embodiment of the present invention.

The macro BS transmits a control signal for network operation to a mobile station and a plurality of Femto BSs through a wireless channel, and the plurality of Femto BSs receive a control signal from the macro base station to determine an operation state, and network The control signal for operation is provided to the macro base station and a terminal managed by the user through a wireless channel. At this time, the macro BS configures mapping information using at least one of the BS-ID, the transmission power, the DCD CCC, and the UCD CCC used by the plurality of femto BSs, and shares the mapping information with the plurality of femto base stations. Then, when receiving a handover request from the terminal, the handover is performed by using one of the femto cells as a target base station using the mapping information. At least one of the BS-ID, the transmit power, the DCD CCC, and the UCD CCC includes information on basic configuration parameters for a SON obtained from a SON server or a management server when the BS initializes. do.

A macro BS performs a handover using one of the femto cells as a target base station using the mapping information as follows.

In a handover using one of a plurality of Femto / Pico BSs as a target base station in a macro BS, as shown in FIGS. 5A and 5B, the BS-IDs are different, but the frequency domain, transmission power, DCD CCC, UCD If the CCCs are the same, a handover can be performed from a macro BS including BS-ID x1 to a Femto / Pico BS including BS-ID x 2.

Similarly, as shown in (c) and (d) of FIG. 5, if the BS-IDs are different, but the frequency domain, transmission power, DCD CCC, and UCD CCC are the same, the BS-ID in the macro BS including BS-ID x 3 Handover to Femto / Pico BS with x 4 is possible. As shown in (e) and (f) of FIG. 5, if the BS-IDs are different, but the frequency domain, transmit power, DCD CCC, and UCD CCC are the same, BS-ID x 6 in a macro BS including BS-ID x 5 Handover to Femto / Pico BS including

Macro BS uses the same BS-ID in order to minimize BS-ID usage in an environment where two base stations are separated from each other, no interference, or no handover. However, when two base stations are in close proximity to each other, there is interference, or a handover occurs, the Macro BS may use two BS-IDs, do not use the same power, or use different frequencies in FIG. 5.

On the other hand, when the UE does not know the transmission power of the BS correctly, the problem of operation during handover is as follows.

The terminal needs to estimate the path loss when selecting its transmission power. At this time, information about the transmission power of the BS is needed to calculate the path loss. If the terminal incorrectly knows the transmission power of the BS, the path loss calculation is incorrect, and the power value transmitted by the terminal is incorrectly determined. In this case, it is difficult to provide a normal service to the terminal. Accordingly, in the present invention, a method of managing a frequency band, TX power, DCD CCC, and UCD CCC values that can be used by the Femto / Pico BS is managed by mapping them with the BS-ID.

Macro BS의 이웃 정보 효율적 획득 방식Efficient Acquisition of Neighbor Information in Macro BS

In the present invention, the Macro BS manages the BS-ID used by the Femto BS / pico BS by mapping values such as transmission power, DCD CCC, and UCD CCC. Macro BS interworks with Femto / pico BS or Femto management server if it manages mapping information about BS-ID and transmit power, DCD CCC, UCD CCC, etc. used by Femto / Pico BS in the region. You can simply build a neighbor list without In addition, even if the BS changes the air configuration parameters (eg, frequency, transmission power, etc.) of the BS by the SON function, the Macro BS can support the handover without additional communication with the Femto / pico BS.

Claims

In the handover method in a macro base station of a broadband communication system,

Configuring, by the macro base station, mapping information by using base station IDs (BS-IDs) and power related information used by a plurality of lower base stations, and transmitting the mapping information to the plurality of lower base stations;

And when the handover request is received from the terminal, performing a handover of one of the plurality of lower base stations to a target base station by using the mapping information.
A macro base station apparatus for performing handover in a macro base station of a broadband communication system,

When mapping information is configured by using base station IDs (BS-ID) and power related information used by a plurality of lower base stations, the mapping information is transmitted to the plurality of lower base stations, and a handover request is received from a terminal. And a controller for performing a handover of one of the plurality of lower base stations as a target base station using the mapping information.
In each of the method of claim 1 and the apparatus of claim 2,

The mapping information may further include one of a frequency band, a downlink channel descriptor (DDC), and an uplink channel descriptor (UCD).
In each of the method of claim 3 and the apparatus of claim 3,

The lower base station is characterized in that the indoor base station that is responsible for the femto cell (femto cell).
In each of the method of claim 4 and the apparatus of claim 4,

When the BS-ID is different between the macro base station and the femto base station which becomes the target base station, and the frequency band, the information related to the power, the DCD, and the UCD are the same,

The macro base station performs the handover to the femto base station.
In each of the method of claim 4 and the apparatus of claim 4,

The macro base station selects the BS-ID so that coverage does not overlap with each other by using a self organization network (SON) function.
In each of the method of claim 4 and the apparatus of claim 4,

The mapping information maps the BS-ID to at least one of a frequency band available to the femto base station, information related to the power, the DCD, and the UCD.
A handover method in a lower base station of a broadband communication system,

Receiving, from the macro base station, the mapping information configured by the lower base station using information related to a base station ID (BS-ID) and power of the macro base station managing the lower base station;

And when the handover request is received from the terminal, handover from the macro base station to the lower base station using the mapping information.
In a handover device in a lower base station of a broadband communication system,

When the base station ID (BS-ID) of the macro base station managing the lower base station and information related to power are received from the macro base station, and the handover request is received from the terminal, the mapping information is received. And a controller for controlling handover from the macro base station to the lower base station.
In each of the method of claim 8 and the apparatus of claim 9,

The mapping information may further include one of a frequency band, a downlink channel descriptor (DDC), and an uplink channel descriptor (UCD).
In each of the method of claim 10 and the apparatus of claim 10,

The lower base station is characterized in that the indoor base station that is responsible for the femto cell (femto cell).
In each of the method of claim 11 and the apparatus of claim 11,

And if the BS-ID is different between the macro base station and the femto base station serving as the target base station, and the frequency band, the power related information, the DCD, and the UCD are the same, the base station is handed over to the femto base station.
In each of the method of claim 11 and the apparatus of claim 11,

The BS-ID is selected by the macro base station so as not to overlap coverage with each other by using a SON (Self Organization Network) function.
In each of the method of claim 11 and the apparatus of claim 11,

The mapping information may be mapped to at least one of a frequency band that can be used by the femto base station, information related to the power, the DCD, and the UCD, and the BS-ID.